1. Field of the Invention
The present invention relates to a kinetic liquid energy reduction system for reducing the level of hydraulic hammer, and more particularly to such a system for use in tank vehicles transporting liquids such as for example railroad tank cars, and even more particularly to such a system wherein a baffling, energy dissipation device having a series of alternating, angled plates in the interior of a pipe-like body is utilized in combination with a rupture disk or plate in order to diminish the potentially disastrous effects of hydraulic hammer action. This is a phenomenon which occurs when for example a railroad tank car loaded with liquid becomes subjected to an abrupt increase or decrease in speed, and which, if unchecked, may cause a catastrophic failure or fracture of the tank.
2. General Background of the Invention
Moving vehicles carrying a liquid load in a tank, such as for example railroad tank cars, when carrying liquids, must cope with problems associated with hydraulic hammer action, a phenomenon which occurs when a liquid in a confined area is subjected to an abrupt increase or decrease in speed.
The resulting kinetic energy produced by the moving liquid inside the container (in the case of a railroad tank car) must either:
(1) be released in some manner from the container; or
(2) be absorbed by some device other than the container itself.
The railroad tank car, which typically has a tank capacity of twelve to fifteen thousand gallons, is often unable to absorb the resulting kinetic liquid energy caused by hydraulic hammer action, and, unless some means is employed whereby the energy is diminished or released from the unit, the tank car itself will fracture, causing destruction of the tank and the loss of the load to the ambient, which in the case of for example toxic chemicals can be an environmental disaster.
The considerable expenses and dangers which could result from hydraulic hammer action in railroad tank cars include catastrophic unit failure, which would occur if the tank fractured to such an extent so as to render it irreparable, or, in a lesser case, simple fracture, a fracture of repairable proportions. However, both types of fractures could result in a spill of varying degrees, including the possible release of toxic liquids and gases into the atmosphere and the surrounding areas, and the considerable expense and danger associated with clean up and repair.
In attempting to deal with the problems associated with hydraulic hammer action in for example railroad tank cars, the railroads and associated carriers have traditionally employed the first method of dealing with the resulting kinetic liquid energy, that is, allowing excess energy to escape from the tank car itself before the greater damage of tank failure could occur. In order for the energy to escape (which was in the kinetic form of the movement of the liquid mass), a rupture disk and an associated liquid escape system was affixed to the top of the tank car.
This prior art liquid escape system is effectively a relief drain which allows a relatively small amount or part of the total liquid load to escape into the atmosphere and surrounding area, thereby relieving the excessive pressure.
The rupture disk is a wafer type disc which, under normal conditions, would seal the contents of the tank from the relief drain, thereby preventing the contents from escaping. However, under conditions of severe pressure, such as those caused by hydraulic hammer action, the rupture disk ruptures, allowing the liquid to pass to the relief drain and out of the tank, thus releasing the excessive pressure and saving the tank and the balance of the liquid load.
A problem associated with the rupture disk system, however, is that when a disk ruptures a replacement rupture disk must be installed, entailing considerable time delay and expense. An additional and potentially more dangerous and damaging problem associated with the rupture disk system is that it is likely that a least a minor spill of the contents of the tank would have occurred in the release of the pressure, thereby contaminating the atmosphere or surrounding area. Such environmental spill or contamination has resulted in a rash of litigation and substantial expense.
The rationale in utilizing such a system was that it was better to incur the relatively minor expense and danger associated with disk replacement and a minor spill than to have incurred the extensive expense and danger of tank car fracture and/or a major spill. However, as indicated, this has been far from a satisfactory solution and situation.